When Brady and Earl are being pulled by the Graboid in their truck, the camera zooms in to Brady, and you see the Graboid pulling the truck backwards. If you look carefully, you'll see that there are tire tracks already on the ground where the truck is being pulled.

I also noticed something else about this stupid film... The creatures can only see heat, right? Well at night it makes sense. Not during the day!! With the hot blazing sun and metal water tower and bulldozer, the creatures would've been attacking EVERYTHING METAL!! The sun would've heated up the buildings and the creatures wouldn't have known what was human or not..